Method of making insulating material



Patented Nov. 4, 1947 OFFICE METHUD OF MAKING INSULATING MATER Ezekiel 3. Jacob, Brooklyn, N. Y.

No Drawing. Application May 1, 19%,

Serial No. 533,663

My present invention relates to insulating materials and more particularly to electrical insulating materials containin micaceous substances, such as mica scales.

It is an object of my present invention to provide composite micaceous materials and articles having high dielectric strength in one direction and small dielectric strength in another.

It is another object of my present invention to provide mica containing materials and articles of variable thermoconductivity, i. e. materials and articles transferring heat differently in various directions.

It is a further object of my present invention to provide improved micaceous materials and articles made therefrom.

With the above objects in view, my present in ventlon mainly consists of an insulating material comprising a binder base and parallelly oriented flakes of a mlcaceous substance embedded in this binder base. It is an important characteristic feature of my invention that these mica flakes are very small in size, having a diameter invention waste mica splittings which are too small to be used as insulating material; this waste mica is pulverized by crushing, grinding or otherwise to a fineness of mesh or finer. The single particles of the thus prepared mica powder are still flake-shaped.

I have found that by incorporating such minute mica flakes parallelly oriented into a binder substance, I obtain a composition which has different dielectric strength and different thermocouductivity in different directions. That means that the dielectric strength is substantially higher normal to the direction of orientation of the mica flakes than in the direction of such orientation. Contrary thereto, the thermcconductivlty of the composition in the direction of parallel orientation of the mica flakes is substantially greater than in direction normal to the same,

I have found that best results are obtained with my new micaceous material if the same contains at least 30% of a binder material; that means that my new insulating material should not contain more than 70% of minute mica flakes. Only if these proportions are maintained, i. e. if my new material contains 30% or more of binder, it is possible to attain proper parallel orientation or the single mica flakes.

I wish to note that in the description and claim I use the term "mica flakes for the insulating 1 Claim. "(CL 154-25) iii material incorporated into my new insulating composition; this definition has to be understood broadly and is intended to include also substances designated usually as mica powder, mica splittings or mica scales; this term should also be understood to cover powder, scales, flakes or splittings of other micaceous or mica-like substances,

such as various other natural silicates having physical characteristics similar to those of mica.

I also wish to stress that I may use the most different organic-or inorganic binders for the purposes of my present invention and thus the term binder as used in the description and claims is intended to include all binders used for such purposes.

The most difierent insulating articles may be made of my new insulating composition. Thus, for instance, it is well adapted to be used for insulating sheets or plates. In this case, all parallelly oriented mica. scales are either parallel or normal or at a certain angle to the faces of the sheets or plates. It is evident that orientation of the mica scales in different directions will produce sheets or plates having entirely different electric and other physical characteristics. Thus, for instance, a sheet in which the mica particles are arranged parallel to the faces 01 the sheet will have a much greater dielectric strength normal to the sheet than a sheet in which the particles extend normal to these faces. Contrary thereto, the thermoconductlvity normal to the faces will be much greater in case the scales are arranged normal to these faces than if they are parallel thereto.

To produce an insulating composition having parallelly oriented minute mica scales embedded therein is rather difficult. I have found that the difiiculties of producing such a, composition are best overcome by parallelly orienting the scales of the mlcaceous substance while they are embedded in a binder base which is in such state as to enable movement of the scales in the binder base. For this purpose, it is preferable to use the binder base in liquid or semi-liquid state.

I have furthermore found that it is of great importance that the influence which is exerted in order to parallelly orient the mica flakes is continued while the binder is hardening. If this is not done, the mica particles in the liquid or semi-liquid binder would lose their parallel orientation.

Various methods can be used in order to obtain parallel orientation of the mica flakesz' Thu it is for instance possible to first prepare a mixture of a semi-liquid binder base and minute mica flakes embedded therein and then to expose this mixture to an electrostatic fleld under the influence oi which the mica flakes will be parallelly oriented in the'binder base. 'I'hereaiter, the binder is hardened and a composition is obtained consisting oi a hardened binder containing embedded therein parallelly oriented mica flakes. 'As explained above, it is important to continue the orienting influence-in the present case the influence oi the electrostatic field-while the binderis being hardened. e. g.

Y dried, so as to ensure proper parallel orientation oi the flakes in the flnished composition.

Instead or using an electrostatic fleld ior the purposes or the present inyention, I might also subject the semi-liquid binder-mica mixture to the influence or electrical high-irequency oscillations, e. g. supersonic oscillations which have also an orienting eiiect upon the mica particles movably embedded. e. a. floating, in the liquid or semi-liquid binder. Also in this case, it is oi importance to continue action oi the high-frequency insulating materials diiiei'ing irom the types described above.

While I have described the invention as embodied in micaceou insulating materials and processes oi producing the same, I do not intend to be limited to the details shown. since various modifications and changes may be made without departing in any way from the spirit of my invention.

. Without iurther analysis, the ioregoing will so iully reveal the gist oi my invention that others can, by applying current knowledge; readily adapt it 10: various applications without omitting Isaoscillations during hardening oi the binder base.

tures that. from the standpoint oi prior art, iairly constitute essential characteristics of the generic or speciflc'aspects oi this invention, and thereiore such adaptations should and are intended to b comprehended within the meaning and range, oi equivalence oi the following claim.

What I claim as new and desire to secure by Letters Patent is: I

In the process 01' forming an insulating ma-- terial of the character described, the steps of preparing an at least semi-liquid mixture of a. hardenable electrically non-conductive binder and minute mica flakes floating therein, exposing said semi-liquid binder-mica mixture to an Similar eiiects can be obtained by drawing the plastic binder containing the mica flakes; during thi process, the flakes are oriented parallelly to the direction oi drawing and thus aiter hardening are embedded in the hardened binder parallelly to each other.

Finally, it is also possible to parallelly orient the mica flakes by extruding the plastic bindermica mixture in which case the flakes will be oriented parallelly to the direction oi extrusion.

I wish to note that although I have described above various embodiments oi my new process, I have found that best results are obtained by sub- Jecting a liquid or semi-liquid binder-mica mixture to an orienting influence, preferably an electrostatic fleld, as described above.

It will be understood that each of the elements described above. or two or more together, may also flnd a useiul application in other types oi 45 Number Name Date 389,519 Lee Sept. 11, 1888 2,286,569 Pollack June 16, 1942 2,384.541 Fruth Sept. 11, 1945 so FOREIGN PATENTS Number Country Date 2,287 Great Britain 1900 553,104 Great Britain May 7, 1943 electrostatic fleld adapted to parallelly orient said minute mica flakes in said semi-liquid hardenable electrically non-conductive binder, and hardening said semi-liquid hardenable electrically nonconductive binder while said binder-mica mixture is still exposed to said electrostatic field, thus obtaining an insulating material consisting of a. hardened electrically non-conductive binder and parallelly oriented minute mica. flakes embedded therein.

. EZEKIEL J. JACOB.

REFERENCES CITED The iollowing references are oi record in the ills of this patent:

UNITED STATES PATENTS 

